In /boot/config.txt:
# BEGIN kbob 2019-03-25 configure soft power GPIO
dtoverlay=gpio-shutdown,gpio_pin=17,active_low=1,gpio_pull=up
dtoverlay=gpio-poweroff,gpiopin=4,active_low=1,export=1
# END kbob 2019-03-25
Some of those parameters are probably not needed.
Some of the caps I specified are not available.
Specifically, Digikey is out of these two.
445-8047-1-ND 47uF 25V 1206
490-1517-2-ND 0.22uF 50V 0603
And I incorrectly specified some 15V caps for components that are expected to see 17V.
And Digikey does not carry NIC caps.
And it has been suggested that I use electrolytic caps instead of some of these.
Nominal cell voltage is 3.7V. Min is 3.3V; max is 4.2V.
Assume 4 cells.
>>> vv = 3.3, 3.7, 4.2
>>> [4 * v for v in vv]
[13.2, 14.8, 16.8]So nominal battery voltage is 14.8V, min and max are 13.2 and 16.8V.
Rent / Renb = (Vin_uvlo / 1.18V) - 1
Rent / Renb + 1 = Vin_uvlo / 1.18V
1.18V * (Rent / Renb + 1) = Vin_uvlo
1.18V * (68K / 6.8K + 1) = 12.98V
So it will shut off when battery voltage drops below 12.98V.
Use RFBT = 5.90Ω and RFBB = 1.07Ω.
V0 = 0.8V * (1 + RFBT / RFBB)
V0 = 0.8V * (1 + 5.90 / 1.07)
V0 = 5.21V
That's a healthy 5V. (-:
(See datasheet section 8.2.2.2.7.)
Minimum on time is 150ns.
RON >= VIN(MAX) * 150ns / (1.3 * 10^-10)
RON >= 16.8 * 150e-9 / 1.3e-10 = 19384
TON = (1.3 * 10^-10 * RON) / VIN
WEBENCH uses 110K for RON. That gives TON = 966nsec. Is that good? Is that bad?
All parameters are from WEBENCH.
Bourns MF-MSMF250/16X-2
as used on Raspberry Pi 3 Model B+
LittelFuse 30R400UMR
Better: LittelFuse NANOSMD400LR-C-2
12V, 4A, 1206 SMT
Panasonic EEU-FC1C182S
1800µF 16V 3000hours low ESR
George I. recommended this one.
Panasonic also makes some slightly shorter SMD caps.
Panasonic EEU-FS1C511
510uF, 16V, 6000 hours
13mm high by 8mm diameter
Digikey filtered list
https://www.digikey.com/short/p347pv
Molex SL connector for Raspberry Pi. 070553-30001 receptacle (right-angle, through hole, 2pos) 50-57-9402 connector (2pos, crimp) 16-02-0103 socket contacts (22-24AWG, gold) mini-PV connector for Pi pins for mini-PV
JST B2PS-VH for panel outputs. JST VHR-2N for cables JSR VHR-4N for LED panel end Plus crimp connectors. JST SVH-21T-P1.1
QTY DK-PART MANUFACTURER MFR PART
25 HHKC16H-ND Assmann WSW AWP 16-7240-T
30 F9967CT-ND LittelFuse NANOSMD400LR-C-2
10 MF-MSMF250/16X-2CT-ND Bourns MF-MSMF250/16X
30 P122389-ND Panasonic EEU-FS1C511
30 455-1648-ND JST B2PS-VH(LF)(SN)
30 455-1183-ND JST VHR-2N
30 455-1185-ND JST VHR-4N
250 455-1133-1-ND JST SVH-21T-P1.1
XXX need horizontal sockets. Five line items(!)
6 WM4900-ND Molex 07055-30001
10 WM2900-ND Molex 50-57-9402
25 WM2512-ND Molex 16-02-0103
10 609-2380-ND Amphenol ICC 69176-006LF
50 609-4518-ND Amphenol ICC 47745-001LF
http://tech.mattmillman.com/info/crimpconnectors/
Here's some good reading material I've saved links to over the years. I use Evernote to store web pages and info so here's some of what I've tagged. I don't mean to flood you with information but at the time I read these I felt they were good enough to save so I'm just sharing. Probably should create some web page and organize them but oh well. Would be nice to pull relevant info out of each and make 1 general reference page as I'm sure there is a ton of repeat information here.
muRata
Analog Devices
TI
AVX
TI Blog
TI App Note
TI Analog Journal
TI Analog Engineer's Pocket Reference
AVX TAP/TEP Technical Summary and Application Guidelines
Chris Reynolds - Parasitics & Capacitor Selection
TI Controlling Output Ripple
Maxim,